Copy/Paste dialog doesn't seem to work

The dialog we previously showed on Ctrl+C doesn't seem to work (at least in Firefox) anymore. I think this has nothing to do with our changes, more something like browser updates.

The relevant function is:

export function onCopyOrPasteHotkey(handler) {
    document.querySelector("textarea.term_textarea").addEventListener("keydown", event=>{
        if(event.ctrlKey && (event.key == "c" || event.key == "v")) {
            handler()
        }
    })
}

I've logged the events and we aren't receiving an event for Ctrl+C or Ctrl+V anymore. There is one for Ctrl, but none for Ctrl+C. This is weird.